This invention relates to improvements in devices for forming shear keyways on the sides of extruded slabs formed on a continuous basis on an extruding type machine.
U.S. Pat. No. 3,740,176, which is made of record in this application, illustrates a machine which forms shear keyways in the form of indentations in the sides of the slabs, by means of an endless flexible belt extending through the side walls adjacent the packing chamber and indenting the plastic concrete as it is being formed and compressed.
When the slabs are placed in side by side relationship, grout is forced between the slabs and fills the keyways thus bonding the slabs together and preventing relative longitudinal movement between adjacent slabs.
Unfortunately, it has been found that the further compaction and treatment of the concrete as the slab is formed, tends to distort these shear keyways which are formed in the sides of the slab thus lessening the efficiency thereof.